android.util.Xml 分析
/**
* api 23 的源码
*/
public class Xml {
/** @hide */ public Xml() {}
/**
* {@link org.xmlpull.v1.XmlPullParser} "relaxed" feature name.
* @see <a href="http://xmlpull.org/v1/doc/features.html#relaxed">
* specification</a>
*/
public static String FEATURE_RELAXED = "http://xmlpull.org/v1/doc/features.html#relaxed";
/**
* Parses the given xml string and fires events on the given SAX handler.
*/
public static void parse(String xml, ContentHandler contentHandler)
throws SAXException {
try {
XMLReader reader = new ExpatReader();
reader.setContentHandler(contentHandler);
reader.parse(new InputSource(new StringReader(xml)));
} catch (IOException e) {
throw new AssertionError(e);
}
}
/**
* Parses xml from the given reader and fires events on the given SAX
* handler.
*/
public static void parse(Reader in, ContentHandler contentHandler)
throws IOException, SAXException {
XMLReader reader = new ExpatReader();
reader.setContentHandler(contentHandler);
reader.parse(new InputSource(in));
}
/**
* Parses xml from the given input stream and fires events on the given SAX
* handler.
*/
public static void parse(InputStream in, Encoding encoding,
ContentHandler contentHandler) throws IOException, SAXException {
XMLReader reader = new ExpatReader();
reader.setContentHandler(contentHandler);
InputSource source = new InputSource(in);
source.setEncoding(encoding.expatName);
reader.parse(source);
}
/**
* Returns a new pull parser with namespace support.
*/
public static XmlPullParser newPullParser() {
try {
KXmlParser parser = new KXmlParser();
parser.setFeature(XmlPullParser.FEATURE_PROCESS_DOCDECL, true);
parser.setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES, true);
return parser;
} catch (XmlPullParserException e) {
throw new AssertionError();
}
}
/**
* Creates a new xml serializer.
*/
public static XmlSerializer newSerializer() {
try {
return XmlSerializerFactory.instance.newSerializer();
} catch (XmlPullParserException e) {
throw new AssertionError(e);
}
}
/** Factory for xml serializers. Initialized on demand. */
static class XmlSerializerFactory {
static final String TYPE
= "org.kxml2.io.KXmlParser,org.kxml2.io.KXmlSerializer";
static final XmlPullParserFactory instance;
static {
try {
instance = XmlPullParserFactory.newInstance(TYPE, null);
} catch (XmlPullParserException e) {
throw new AssertionError(e);
}
}
}
/**
* Supported character encodings.
*/
public enum Encoding {
US_ASCII("US-ASCII"),
UTF_8("UTF-8"),
UTF_16("UTF-16"),
ISO_8859_1("ISO-8859-1");
final String expatName;
Encoding(String expatName) {
this.expatName = expatName;
}
}
/**
* Finds an encoding by name. Returns UTF-8 if you pass {@code null}.
*/
public static Encoding findEncodingByName(String encodingName)
throws UnsupportedEncodingException {
if (encodingName == null) {
return Encoding.UTF_8;
}
for (Encoding encoding : Encoding.values()) {
if (encoding.expatName.equalsIgnoreCase(encodingName))
return encoding;
}
throw new UnsupportedEncodingException(encodingName);
}
/**
* Return an AttributeSet interface for use with the given XmlPullParser.
* If the given parser itself implements AttributeSet, that implementation
* is simply returned. Otherwise a wrapper class is
* instantiated on top of the XmlPullParser, as a proxy for retrieving its
* attributes, and returned to you.
*
* @param parser The existing parser for which you would like an
* AttributeSet.
*
* @return An AttributeSet you can use to retrieve the
* attribute values at each of the tags as the parser moves
* through its XML document.
*
* @see AttributeSet
*/
public static AttributeSet asAttributeSet(XmlPullParser parser) {
return (parser instanceof AttributeSet)
? (AttributeSet) parser
: new XmlPullAttributes(parser);
}
}
先看3个重载的parse方法
public static void parse(String xml, ContentHandler contentHandler);
public static void parse(Reader in, ContentHandler contentHandler);
public static void parse(InputStream in, Encoding encoding, ContentHandler contentHandler) ;
根据输入的类型 有String, Reader , InputStream 三种, InputStream还必须指定文本编码方式,
对输入的xml来源封装成InputSource对象,
对Xml的处理生成一个ExpatReader 对象, 这个继承自XMLReader
解析则是调用XMLReader.parse(InputSource)来解析
2. InputSource 对象 就是一个javaBean, 位于 org.xml.sax包下
几个属性:
private String publicId; private String systemId; private InputStream byteStream; private String encoding; private Reader characterStream;
3. ExpadReader 对象 ,位于 org.apache.harmony.xml包
有一个静态内部类 Feature ,标识 xml的uri
private static class Feature {
private static final String BASE_URI = "http://xml.org/sax/features/";
private static final String VALIDATION = BASE_URI + "validation";
private static final String NAMESPACES = BASE_URI + "namespaces";
private static final String NAMESPACE_PREFIXES = BASE_URI + "namespace-prefixes";
private static final String STRING_INTERNING = BASE_URI + "string-interning";
private static final String EXTERNAL_GENERAL_ENTITIES
= BASE_URI + "external-general-entities";
private static final String EXTERNAL_PARAMETER_ENTITIES
= BASE_URI + "external-parameter-entities";
}
方法:
//判断name 是不是对应于 Feature中的uri标识,不是则false
public boolean getFeature(String name);
//设置uri的标识的bool值
public void setFeature(String name, boolean value);
// 如果 name.equal("http://xml.org/sax/properties/lexical-handler")才返回一个lexicalHandler,否则报错
public Object getProperty(String name);
//同getProperty()只能设置LEXICAL_HANDLER_PROPERTY的, value 强转成LexicalHandler
public void setProperty(String name, Object value);
//几个set,get方法:
setEntityResolver(resolver);
getEntityResolver(resolver);
//XXX代表:DTD, Content, Error, Lexical
setXXXHandler(handler);
getXXXHandler();
//重点的parse方法
private void parse(Reader in, String publicId, String systemId);
private void parse(InputStream in, String charsetName, String publicId, String systemId);
public void parse(String systemId);
不管是InputStream还是Reader,都是生成一个 ExpadParser对象,调用expadParser.parseDocument();来解析
4 . ExpatParser同样位于 org.apache.harmony.xml包中, 这个才是解析xml的main方法
void parseDocument(InputStream in) throws IOException, SAXException {
startDocument();
parseFragment(in);
finish();
endDocument();
}
5. 还有一个ContentHandler 接口 , 在org.apache.harmony.xml包中,
在调用Xml.parse()时作为第二个参数传递进来的, 这个传递给了XMLReader的
setContentHandler(contentHandler)方法, 作为XMLReader的一个属性
然后在XMLReader.parse()时,生成的ExpatParser时,XMLReader作为一个参数传递给了ExpatParser,
在ExpatParser调用parseDocument时,
在执行方法startDocument(), endDocument()其实都是要调用 contentHandler的方法startDocument(), endDocument()
关于ContentHandler的详细方法,可见
http://blog.csdn.net/buaalei/article/details/6052061
这个Xml对象的使用就是SAX解析, 只是比较简单, 同时主要是实现接口ContentHandler,
这儿有个例子可供参考 http://sinye.iteye.com/blog/763895.